Home>Discussions>EXTERIORS>6" by 6" cedar posts and risk of rotting when sitting them on to of concrete footings
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jarliss1
6" by 6" cedar posts and risk of rotting when sitting them on to of concrete footings

my hew house's exterior deck rests on 8 6" by 6" cedar posts. Each cedar post rests on 12" concrete footings, which extend 12" above grade. my concern is that the cedar will rot where it sits on the flat top of the concrete footing. The concrete footing is 12" in diameter. Do i need to install post braces on the bottom of each cedar post, which keeps the bottom of the post 2" above the concrete surface?
i also intend to cover over the footings and bottom 6" of cedar post with a dry-laid wall. This will covering up will increase the chance of rot and also prevent me from inspecting the posts. Any advice?

A. Spruce
Re: 6" by 6" cedar posts and risk of rotting when sitting them on to of concrete foot

The posts should not be in direct contact with the concrete, as they will wick moisture from the concrete and rot from the bottom up. Typical post bases have a metal plate that holds the posts 1" above the concrete so that they stay dry.

Dry stacking stone around the posts will slightly increase their susceptibility to rot, however because it's dry stacked, the posts will be able to breathe so that any moisture that gets in will eventually find it's way back out.

HoustonRemodeler
Re: 6" by 6" cedar posts and risk of rotting when sitting them on to of concrete foot

What Spruce said plus;

If the bottoms of the posts were cut, then they should be re-sealed with something to prevent water from wicking up. Down here in termite-ville, we also add sheet metal termite pans atop the ceement piers.

jkirk
Re: 6" by 6" cedar posts and risk of rotting when sitting them on to of concrete foot

another thing you can do is if your are going to run a trim around the base of the post is to do so with grk exterior trim screws. basically a torx bit screw with a very small head. you can also wrap the bottom of the post with either vycor or scraps of ice and water sheild.

ordjen
Re: 6" by 6" cedar posts and risk of rotting when sitting them on to of concrete foot

I built a pergola 3 years ago which sits freely on my concrete patio. Before setting the 6X6 douglas fir corner posts, I fiberglassed the base of the posts. Further, just as I erected the posts, I put a piece of seam-seal (closed cell foam intended for under a sill plate on a foundation wall)under it.

I finally put a decorative wooden base around the bottom of the post. The trim does not contact the concrete. I sawed a small kerf into the bottom edge of this base trim. This aides in keeping rain water from getting to the base of the post. All surfaces of the post and the trim boards were primed and painted before I fastened them together. I am confident it will outlast me, but then I am an old f..t! :)

The pergola can be seen on YouTube by typing in "pergola pandering"

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